HIV pre-exposure prophylaxis (PrEP) use may lead to higher STI incidence via behavioural risk compensation. We examined changes in sexual behaviour between baseline and 6 months after PrEP initiation among MSM and transgender women (TGW).Design:
Prospective, open-label demonstration study at a large sexually transmitted infection (STI) clinic in Amsterdam, the Netherlands.Methods:
Participants answered questions about sexual behaviour in the preceding 3 months, including number of anal sex partners and frequency of anal sex with and without condom by partner type and were tested for STI. Sexual behaviour at baseline was compared with 6 months after PrEP initiation using Wilcoxon signed rank tests. Logistic regression was used to identify factors associated with an increase in receptive condomless anal sex acts (rCASa) with casual partners.Results:
Data were available for 328 (99%) MSM and 2 (1%) TGW. The number of receptive and insertive condomless anal sex acts (CASa) increased (baseline: median 11, interquartile range 4–23; 6 months: median 14, interquartile range 6–26, P < 0.001), whereas the number of anal sex partners (P = 0.2) and anal sex acts (P = 0.8) remained unchanged. Prevalence of STI was stable. Older age, prior engagement in chemsex, recent use of postexposure prophylaxis and choosing a daily PrEP regimen at baseline were associated with an increase in rCASa with casual partners.Conclusion:
Over the first 6 months after initiation of PrEP, an increase in insertive and receptive CASa with casual partners was observed. Long-term follow-up data are needed and STI incidence needs to be closely monitored.